Get your kids tested to see if he/she has antibodies to casein. That is the protein in milk. If that comes back as positive, your kid probably has a leaky gut, caused by sugar and excess carbs or starches (which break down into sugar) and have weakened the gut lining, allowing the protein to enter the blood stream before being broken down, causing a response from the immune system. You'll need to mega dose the kid with Vitamin D (50,000 IUs per day for a couple of weeks at least along with some vitamin K2, zinc and copper would be good too) and switch the kids diet over to all meat. Make sure it is grass raised, grass finished beef that was raised without hormones, steroids or vaccines. For cooking, use beef tallow (preferably from the same animal). DRINK LOTS OF WATER. Feed your kid lots of eggs (high quality, free range etc, you'll know they're good by how bright yellow they are without the use of added chemicals, you might need to check your local farmers market) like 8 eggs per day. Don't look so much at the cost of this, when you eat like this, you stay full for a long time, and don't need snacks. Feed your kid say 8 eggs in the morning with some good quality bacon, and they won't be hungry until dinner. Then feed the kid some good beef cooked in tallow. I don't know if your kid will ever get over the dairy allergy, but you'll notice a lot of good changes in as little as a few days. If your kid does have a leaky gut, it is best to avoid the nut butters as they contains lectins, which you don't want wearing out the gut more or passing right into the blood stream. Nut allergies are usually quite severe, so best to avoid forming one.